This section of IEC 61000-4 gives a functional and design specification for flicker measuring apparatus intended to indicate the correct flicker perception level for all practical voltage fluctuation waveforms. Information is presented to enable such an instrument to be constructed. A method is given for the evaluation of flicker severity on the basis of the output of flickermeters complying with this standard.

This section is based partly on work by the “Disturbances” Working Group of the International Union for Electroheat (UIE), partly on work of the IEEE, and partly on work within IEC itself. The flickermeter specifications in this section relate only to measurements of 230 V, 50 Hz inputs and 120 V, 60 Hz inputs; specifications for other voltages and other frequencies are under consideration.

-Records voltage fluctuations.
-Converts voltage changes to an estimate of light variation from an incandescent bulb.
-Weights this estimate according to frequency to account for human perception.
-Determines an instantaneous flicker perceptibility reading (Pinst).
-Derives a short-term flicker indication (Pst) over a 10-min period.
-Derives a long-term flicker indication (Plt) over a 2-h period.

As a guide, the threshold of flicker perception at about 8 Hz for half the population is only 0.3% relative modulation. This means that accurate, high-resolution voltage measurement is a prerequisite to good flicker measurements. The range of threshold levels across a wide frequency up to about 15 Hz is collectively described by Pst = 1 or the threshold of irritability.